We plan to further develop the in vitro suppressor cell system by characterizing the T cell subsets involved. We will attempt to produce and isolate donor specific suppressor cells and factors. We propose that the kidney recipient engendered MLC blocking factors are in part, anti-idiotypic antibodies and linked to cellular suppression. It is proposed that both of these mechanisms can ultimately lead to a specific mode of immunosuppression. Three systems will be studied. 1. The human renal transplant recipient, 2. mouse and 3. canine models. 1. The human renal transplant project will continue to envolve prospective immunological monitoring assays of increasing sophistication. We plan to characterize and isolate the T suppressor cell subpopulations generated in MLC before and after transplantation and to compare this with the development of blocking and anti-idiotype antibody. We plan to exploit lymphocyte Fc-receptor properties to separate subpopulations of T lymphocytes and their soluble mediators that function by suppression. We will also employ immunoadsorbent cellular chromatography, elutriation centrifugation and fluorescence-activated cell sorter analysis to further purify and characterize the T lymphocyte subsets. We will attempt to maintain and retrieve the MLC generated suppressor cell sub-populations by continuous culture or cryopreservation. 2. In the mouse work, we will continue to study a skin graft model testing the in vitro effects of administering MLC generated T suppressor cells and/or suppressor factors. These cells will be purified by exploiting the surface markers Ig, Ly antigens, selective lectin affinity and anti-idiotype sera. 3. We have recently developed a lymphocyte islet cell culture reaction (MLIC) demonstrating both tissue specific and allogeneic islet cell immunogenicity in inbred beagles. We have to monitor responses of recipients of allografts of the free draining vascularized segmental pancreases compared with islets of Langerhans (as well as the effects of the administration of suppressor cells generated in vitro on graft survival).